docs: def config_updated_since(self, sentry_unit, filename, mtime,
                               sleep_time=20, retry_count=30,
                               retry_sleep_time=10):
          """Check if file was modified after a given time.
  
          Args:
            sentry_unit (sentry): The sentry unit to check the file mtime on
            filename (string): The file to check mtime of
            mtime (float): The epoch time to check against
            sleep_time (int): Initial sleep time (s) before looking for file
            retry_sleep_time (int): Time (s) to sleep between retries
            retry_count (int): If file is not found, how many times to retry
  
          Returns:
            bool: True if file was modified more recently than mtime, False if
                  file was modified before mtime, or if file not found.
          """
          unit_name = sentry_unit.info['unit_name']
          self.log.debug('Checking that %s updated since %s on '
                         '%s' % (filename, mtime, unit_name))
          time.sleep(sleep_time)
          file_mtime = None
          tries = 0
          while tries <= retry_count and not file_mtime:
              try:
                  file_mtime = self._get_file_mtime(sentry_unit, filename)
                  self.log.debug('Attempt {} to get {} file mtime on {} '
                                 'OK'.format(tries, filename, unit_name))
              except IOError as e:
                  # NOTE(beisner) - race avoidance, file may not exist yet.
                  # https://bugs.launchpad.net/charm-helpers/+bug/1474030
                  self.log.debug('Attempt {} to get {} file mtime on {} '
                                 'failed\n{}'.format(tries, filename,
                                                     unit_name, e))
                  time.sleep(retry_sleep_time)
                  tries += 1
  
          if not file_mtime:
              self.log.warn('Could not determine file mtime, assuming '
                            'file does not exist')
              return False
  
          if file_mtime >= mtime:
              self.log.debug('File mtime is newer than provided mtime '
                             '(%s >= %s) on %s (OK)' % (file_mtime,
                                                        mtime, unit_name))
              return True
          else:
              self.log.warn('File mtime is older than provided mtime'
                            '(%s < on %s) on %s' % (file_mtime,
                                                    mtime, unit_name))
              return False